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Oceans Are Absorbing Almost All of the Globe’s Excess Heat

This year is on track to be the third consecutive hottest year on record. Where does that heat go? The oceans, mostly.

Where the Oceans Have Been Colder and Hotter Than Average

-2°C

0

+2

1900s

1910s

1920s

1930s

1940s

1950s

1960s

1970s

1980s

1990s

2000s

2010s

Average temperatures from each decade compared with the 20th-century average.

Ocean temperatures have been consistently rising for at least three decades. Scientists believe that global sea surface temperatures will continue to increase over the next decade as greenhouse gases build up in the atmosphere.

Natural patterns such as El Niño and La Niña can have year-to-year effects on temperatures. Individual storms can also influence ocean temperatures for months or longer. But the overall temperature trends by decade reveal a backdrop of human-caused warming.

Record High Annual Mean Surface Temperatures, 2015

Last year, nearly all observed ocean surface temperatures registered above average because naturally occurring conditions caused by El Niño combined with human-induced warming. About a quarter of those observations broke record highs.

Heat Accumulates in the Oceans

Since 1955, more than 90 percent of the excess heat retained by the Earth as a result of increased greenhouse gases has been absorbed by the oceans, leaving ocean scientists like Eric Leuliette at the National Oceanic and Atmospheric Administration feeling that 90 percent of the climate change story is being ignored.

Estimated Heat Accumulation

Ocean

Ice Melt

Land

Atmosphere

200

100 zettajoules

1980

1990

2000

2010

Ocean

Ice Melt

Land

Atmosphere

200

100 zettajoules

1980

1990

2000

2010

Ocean

Ice Melt

Land

Atmosphere

200

100 zettajoules

1980

1990

2000

2010

Amounts in zettajoules, or sextillions of joules, relative to 1971 levels.

For several decades, more energy has been absorbed than emitted at the top of Earth’s atmosphere. According to Gregory Johnson, an oceanographer at NOAA, the rate of energy gained between 1971 and 2010 was roughly equal to the power required to run 140 billion 1,500-watt hair dryers over the same number of years. The rate has only increased in the past decade.

This excess energy has largely been sucked up by the oceans, which have a huge capacity to store heat. As the oceans store more heat, however, they expand. Scientists have shown that over the past decade, this thermal expansion has caused about one-third of the rise in sea levels.

What Hotter Oceans Bring

The oceans act as Earth’s enormous heat sponge, sheltering continents and the people who live on them from atmospheric extremes. The near-surface ocean takes only decades to warm in response to elevated greenhouse gas concentrations, but the deep ocean will take centuries to millenniums, raising sea level all the while. In the meantime, warmer ocean temperatures may also increase the destructive potential of extreme weather, like cyclones and hurricanes.

In fact, the effects of warmer waters are already widespread.

Josh Haner/The New York Times

Ice Melt and Sea Level Rise

The Greenland ice sheet is studded with meltwater streams, rivers and lakes. The rate of melt is alarming many scientists. Both ice melt and thermal expansion are causing a significant rise in global sea levels.

Agence France-Presse — Getty Images

Marine Species Are at Risk

Warmer temperatures are threatening some marine animal and plant species, like these bleached coral on the Great Barrier Reef. Scientists also predict that some birds, like the black-legged kittiwakes in Norway, may soon die off in warmer waters.

Bruno C. Vellutini

Habitats Are Changing

The warmer conditions have allowed some jellyfish, like the comb jellyfish, pictured above, in Narragansett Bay, to have longer seasons. Others have expanded their territory. In some cases, United States fisheries have shifted north to cooler waters.

Sources: National Oceanic and Atmospheric Administration (decade averages and 2015 record highs); Intergovernmental Panel on Climate Change (estimated heat accumulation); Lucas Brotz, Institute for the Oceans and Fisheries, The University of British Columbia (jellyfish)